I would like some help with the set-up of my B&W ASW608 sub, which is connected to the AV7701 Marantz Prepro (via a forked RCA-to-2RCA cable --- since the sub has two RCA inputs). Every guide I've read recommends that before running the Audyssey set-up I should set the volume(line) of the sub half-way up. However, even setting it to 40% it starts to hum and sounds like it is being overdriven (the volume of the hum increases proportionally to the line-volume setting). In the end, I set the volume to 20% and on top of that Audyssey calibrated to –7.5dB. This is the setting I am using now.
So, is the Marantz too powerful for the ASW608? Is there danger of destroying my sub? I have recently had the sub's faulty amp replaced (it is known to burn out after a few years), and that cost me a lot of money.